2, 3-dialkoxy-5, 6-p-dioxanethiol s, s-(o, odialkyl phosphorodithioate)



pounds were made by mixing l gram of the residue with 1 ml. benzene and l ml. sorbitan monolaurate polyoxyalkylene derivative (Tween 20). The concentrate was then diluted with water to form dispersions of the residue in water varying in concentration from 1.0% to 0.00025%. The dispersions were then tested for their toxicity to caged insects and to mites not only by spraying theinsects but by spraying the plants alone as well for the purpose of determining residual toxicity. Standard test methods were used for obtaining the results tabulated below. l Y

Tests on systemic activity were carried out by placing a. freshly cut slip of'a pea plant in water containing 50 parts per million of the compound tested for 24 hours and infesting with pea aphids. The per cent kill was determined after 48 hours..

The organic dithiophosphate compounds of this invention have the formula in which each R and R' is the same or a ditferent organic radical such as a lower alkyl radical: methyl, ethyl, n-propyl, isopropyl, isobutyl, sec-butyl and n-butyl, and chlorine substituted lower alkyl radicals. In the above definition of the scope of the compounds of this invention, lower alkyl is defined to include those alkyl radicals with l to 4 carbon atoms.

In producing 2,3-dialkoxy-p-dioxanes from which the insecticidal compounds of this invention are produced, the 2,3-dichlorodioxane is reacted with the alcohol ROH or the corresponding alkoxide ROMe where Me is an alkali or alkaline earth metal. YWhen ROH is reacted with the 2,3#dihalo-pdioxane, hydrogen chloride is liberated and maybe driven off as a gas or it may be sequestered in situ with a suitable sequestering agent such as pyridine, triethylamine, dirnethylaniline, or other tertiary amine. The reaction is conducted in the absence of water to avoid hydrolysis of the halogen on the dioxane ring and the sequestering agent is preferably anhydrous. The sequestering agent may, furthermore, be added gradually during the course of the reaction to avoid causing hydrolysis. As

a further means of effecting complete substitution, an

excess of the alcohol ROH is preferably maintained in the reaction mixture. Moreover, the alcohol can be continu ously distilled off as a means of carrying away the halogen acid which is liberated and fresh alcohol ROH may be added continuously to replace that distilled oi.

2,3-dialkoxyS,6-dichloro-p-dioxane is readily obtained from the 2,3-dialkoxy-p-dioxane by chlorination with chlorine gas at a temperature at which chlorination will take place but below temperatures at which decomposition is noticeable. Chlorination temperatures in the range of 20 to 200 C. are suitable. The chlorination may be carried out in the presence or absence of solvents. When a. solvent is used, suitable solvents include: chloroform, carbon tetrachloride, nitrobenzene and pentachloroethane.

In producing the compounds of this invention, the reaction between the 2,3-dichloro-5,6-dialkoxy-p-dioxane or 2,3-dibromo-S,6-dialkoxy-p-dioxane and the ester of dithiophosphoric acid or its salt is carried out by heating thev two reactants at a temperature at which reaction takes place but below the decomposition temperature in the range of 20 to 200 C., preferably in the range of 30 to 110 C. The reactants may be mixed in any desired order. In order to get complete reaction, it is preferable to use an excess over the theoretical amount of the ester of the dithiophosphoric acid. When the reaction is complete, the excess ester of the dithiophosphoric acid is readily removed by washing with water containing sufcient alkali to produce the water-soluble salt.

The reaction with the ester of dithiophosphoric acid is preferably carried out in nonaqueous media. Organic solvents are desirable to aid in control of the rate of reaction, Suitable solvents include benzene, toluene, xylene, cyclohexane, hexane, anhydrous alcohol solvents and dioxane. It is preferable to use hydrocarbon solvents when using an amine salt of the dithiophosphoric acid ester or when using an amine or ammonia as a sequestering reagent. After the reaction is complete, the solvent is readily removed by distillation.

Vvhen the diester of dithiophosphoric acid is used as the free acid in the reaction with the 2,3-dihalo-5,6dialkoxy p-dioxane, hydrogen halide whichl is liberated is preferably sequestered by adding a material to combine with the hydrogen halide as formed. vIt is convenient to use pyridine for this purpose. However, in its place other tertiary organic amines may be used, and they may be added4 in equivalent amount at thebeginning of the-reaction or gradually during the course of the reaction.

Likewise, the amine can be reacted with the diester of the l dithiophosphoric acid prior to carrying out the reaction with the 2,3-dihalo-S,-dialkoxy-p-dioxane as in the examples. Amines which can be used include pyridine, tertiary alkylamines such as trimethylamine, tributylamine, triamylamine, dimethylaniline, and the like. Inorganic bases may also be used. These include ammonia, alkali metal hydroxides, carbonates and bicarbonates, and alkaline earth metal hydroxides and carbonates.

As in the case of organic bases, the inorganic bases may also be used rst to form a salt of the esterofthe dithiophosphoric acid. When the salt of the ester of dithiophophoric acid is used as the reactant, it is preferable to use a salt which is soluble in the organic lsolvent used for the reaction. The organic salts of amines are particularlysatisfactory because of the good solubility of these salts in the nonreactive hydrocarbon solvents. When the free acid is reacted with the 2,3-dihalo5,6dialkoxy-pdioxane, the alkaline material is preferably added gradually as needed but it can be added all at once if desired.Y Ammonia is suitably added gradually as a gas, the solids ar suitably added in'inely divided form.

The dithiophosphoric acid ester is produced by reacting the lower aliphatic alcohol, which is to form a part of the ester, with P285 preferably in a nonreactive solvent such as benzene, toluene, xylene, hexane or cyclohexane and removing the H28 which is liberated. The reaction is carried out at any temperature in the range of 50 to 120 C., selecting the lowest practical temperature without def composition. If different radicals are desired for the various R radicals, a mixture of alcohols may be used in the production, of thedithiophosphoric acid ester. Likewise, dithiophosphoric acid esters produced from'different alcohols can be mixed for use in the reaction with the 2,3-dihalo-5,*6-dalkoxy-p-dioxane.

The methodslbywhich the products. of this invention are isolated will varyV slightly with the reactants Vused and the product produced. In some instances the chloride salt split out in the reaction separates and can be filtered off. In other instances the chloride salt'is best-removed by washing with water. The excess salt of the ester of dithiophosphoric acid is also removed by the water Wash. The benzene or other solvent is then removed by distillationvleaving an insecticidally active residue. Further purification by selective solvent extraction or by adsorptive agents such as activated carbon, or clays, can precede the removal of the solvent. Likewise, an organic solvent can be added to aid in the purification by adsorptive agents. .Howeven the product is generallyvsatisfactory for tion.

The compounds of this invention are used as the sole toxic agent in pesticidal formulations or in admixture with other toxicants for modification of the properties of l the individual toxicants. They may be used, for example, in admixtureV with toxaphene, DDT, Thanite,

use as a pesticide without further purificachlordane, rotenone, pyrethrin, and the like, in many of the formulations suggested below.

The compounds of this invention are made into pesticidal compositions for use against insects and mites by dilution with an insecticidal adjuvant as a carrier therefor, by dispersing in an organic solvent, or in water, or by diluting with a solid insecticidal adjuvant as a carrier. Dispersions containing a surface-active dispersing agent have the advantage of spreading the toxic substance more effectively over the plant surface. Dispersions in organic solvents include dispersions in alcohols, pint oil, hydrocarbon solvents, difluorodichloromethane, and similar organic solvents. The compounds of this invention are also used in aerosol formulations in which difluoro dichloromethane and similar aerosol propellents form the propellant vehicle.

Aqueous dispersions are made up from the compounds of this invention, a surface-active dispersing agent and water as the essential ingredients. The amount of the compounds of this invention in the aqueous dispersions when diluted for spraying of plants will be in the range of 10.0% to about 0.0001% of the aqueous dispersion.

The aqueous dispersion will ordinarily be made up from a concentrate, and the concentrate will be dispersed in water to the proper concentration for application to the plants to be treated in the field. The concentrate is composed essentially of the compound of this invention and surface-active dispersing agent. The concentrate may also contain sucient organic solvents to aid in effective dispersion. The amount of surface-active dispersing agent used is usually at least of the amount of toxic compound in the concentrate.

Suitable surface-active dispersing agents for use in the compositions of this invention are those disclosed in Chemistry of Insecticides, Fungcides and Herbicides (by Donald E. H. Frear, second edition (1948), pages 280- 287) for use with known insecticides and include neutral soaps of resin, alginic and fatty acids and alkali metals or alkylamines or ammonia, saponins, gelatins, milk, soluble casein, flour and soluble proteins thereof, sulte lye, lignin pitch, sullite liquor, longchain fatty alcohols having 12-18 carbon atoms and alkali metal salts of the sulfatos thereof, salts of sulfated fatty acids, salts 0f sulfonic acids, esters of long-chain fatty acids and polyhydric alcohols in which alcohol groups are free, clays such as fullers earth, China clay, kaolin, attapulgite, and bentonite and related hydrated aluminum silicates having the property of forming a colloidal gel. Among the other surface-active dispersing agents which are useful in the compositions of this invention are the omegasubstituted polyethylene glycols of relatively long-chain length, particularly those in which the omega substituent is aryl, alkyl, or acyl. Compositions of the toxic material and surface-active dispersing agent will in some instances have more than one surface-active dispersing agent for a particular type of utility, or in addition to a surface-active dispersing agent, hydrocarbons such as kerosene and mineral oil will also be added as improvers. Thus, the toxic material may contain a clay as the sole l adjuvant or clay and hydrocarbon, or clay and another surface-active dispersing agent to augment the dispersing action of the clay. Likewise, the toxic material may have water admixed therewith along with the surface-active dispersing agent, suicient generally being used to form an emulsion. All of these compositions of toxic material and surface-active dispersing agent may contain in addition synergists and/ or adhesive or sticking agents.

What I claim and desire to protect by Letters Patent is:

l. As a new composition of matter a compound of the formula in which each R and R represents a radical of the group consisting of lower alkyl and chloro lower alkyl.

2. As a new composition of matter a compound of the formula s Ro-CH oH-siwom),

in which each R represents a radical of the group consisting of lower alkyl and chloro lower alkyl.

3. As a new composition of matter a compound of the formula in which each R represents a radical of the group consisting of lower alkyl and chloro lower alkyl.

5. A pesticidal composition comprising the compound of claim 1 and an insecticidal adjuvant.

6. A pesticidal composition comprising the compound of claim 2 and an insecticidal adjuvant.

7. A pesticidal composition comprising the compound of claim 3 and an insecticidal adjuvant.

8. A pesticidal composition comprising the compound of claim 4 and an insecticidal adjuvant.

References Cited in the le of this patent UNITED STATES PATENTS 2,529,304 Mikeska Nov. 7, 1950 2,531,129 Hook Nov. 21, 1950 2,542,604 Weisel Feb. 20, 1951 2,565,920 Hook Aug. 28, 1951 2,565,921 vHook Aug. 28, 1951 

1. AS A NEW COMPOSITION OF MATTER A COMPOUND OF THE FORMULA 